<!doctype html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>test underscore</title>
</head>
<body>

<script src="underscore-debug.js"></script>

<script>
    var bolt = _.map ({"a":10, "b": "string"}, function(value, index, list) { return  index; });
    console.log(bolt)//['a', 'b']

    var bolt = _.map ({"a":10, "b": "string"}, function(value, index, list) { return  value + 10; });
    console.log(bolt)//[20, "string10"]


</script>

</body>
</html>